1. Field of the Invention
The present invention relates to a locking device for securing an attachment member to a main body and more particularly to a locking device suitable for a reciprocating electric shaver for shaving, for instance, face whiskers (“hair”) by causing an inner cutter(s) to move reciprocally while being pressed against the inner surface of an outer cutter(s) that is substantially inverted-U-shaped when viewed from the side.
2. Description of the Related Art
Reciprocating electric shavers are commonly known. Generally, reciprocating electric shavers are made so that an inner cutter is caused to move reciprocally while it is being pressed against the inner surface of an outer cutter that is substantially inverted-U-shaped when seen from the side, and hair coming through the slits provided in the outer cutter is cut by the reciprocating inner cutter.
Japanese Patent Application Laid-Open (Kokai) Nos. 2004-49864 and H10 (1998)-323461, discloses reciprocating electric shavers, and in these shavers, an outer cutter assembly that is held so that the outer cutter can freely sink in, in the up and down direction, is detachably locked to the shaver main body which houses therein a motor. More specifically, in this shaver, an oscillator is provided in the main body and vibrated by the motor, and the inner cutter is held on the oscillator in such condition that it is capable of swinging and is urged upward by an inner cutter upwardly pushing spring, so that the inner cutter moves reciprocally while being pressed against the inner surface of the outer cutter by a prescribed spring force.
The locking device disclosed in the above relevant art that is for attaching and detaching the outer cutter assembly to and from the main body is designed so that it engages and disengages a push button, provided so that it can be pressed in from the side of the main body and is capable of returning, with engagement pawls provided in the outer cutter assembly. More specifically, a push button return spring is compressed and installed between the push button and parts installed inside the main body, and a return force toward the outside of the main body is imparted to the push button by this return spring, so that a locked condition occurs when the push button is made to return, and the lock is released when the push button is pushed in.
In such a conventional locking device, when assembling the shaver main body, it is necessary to mount the return spring in between the parts installed inside the main body while mounting the push button in the opening of the main body casing. Accordingly, the installation of such parts in the main body and the installation of the locking device must be performed in parallel, making the assembly work of shavers inefficient. This has been a problem.
In addition, the spring load of the push button return spring acts on the inner surface of the main body casing and on the parts installed inside the main body; accordingly, it is necessary to reinforce the positions on the inner surface of the main body casing and on the parts mounted inside the main body where that return spring load acts. For that purpose, reinforcing ribs or hubs must be provided at those positions, and the material of the parts must be large in thickness to enhance their rigidity. When those parts are molded products made of resins (plastics), limitations arise on the shapes of the parts in terms of the structure of the molding dies, and thus design freedom declines, which is also a problem.